[Plugin: Google Maps for WordPress] Doesn't work in Firefox, messed up in Chrome/Safari

On the latest version of WordPress, latest version of Chrome, Safari and Firefox, latest version of this plugin. Mac OSX Snow Leopard.

The map shows up in Chrome and Safari, but the “speech bubble” effect wrapped around the place marked/to enter your address for directions is slightly distorted on the bottom.

The map doesn’t show up at all in Firefox 8, though it does show the speech bubble to enter your address for directions. When I enter an address, it shows the purple line showing the path between destinations, but the map itself isn’t there. It also loads the word directions below the map just fine.